Materials Flashcards
Density
Mass per unit of volume of a material
Volume of a regular solid: Cuboid, Sphere and Cylinder
Cuboid - length x width x height
Sphere - 4/3 x pi x r^3
Cylinder - pi x r^2 x h
Volume of irregular solid
Fill up a eureka can up with water and place the regular solid in it
Measure the volume of displaced water in a measuring cylinder
Volume of water displaced = volume of solid
Hooke’s Law
Extension of a spring is directly proportional to the force applied, up to the limit of proportionality
Force applied (N) = spring constant (Nm) x extension (m)
Spring Constant (k)
Force applied per unit extension
Higher spring constant means?
The stiffer the material
Effective spring constant of springs in parallel?
Ke = K1 + K2 + …
Effective spring constant of springs in series?
1/KE = 1/k1 + 1/K2 + …
Limit of proportionality
The force is proportional to the extension
Elastic deformation
Material returns to its original length when the force is removed
Plastic behaviour
Permanent deformation
Hysteresis
Loss of energy as heat
Equal to the are between loading and unloading curves
Thermal energy lost as heat equals?
Area underneath the loading graph, minus area underneath the unloading graph
Elastic strain energy is …
Energy stored in a spring when stretched
Elastic strain energy (J) =
1/2 x F(N) x Extension (m)
Elastic strain energy is also equal to?
Work done to a stretched wire
Area underneath Force(N) and extension (m) graph is equal to?
Elastic potential energy
Stress
Force per unit cross-sectional area
Tensile stress (Pa) = Force (N)/ Area (m^2)
Strain
Extension of a material per unit original length
Tensile strain = Extension (m)/ original length(m)
No units –> Ratio of two lengths
Young’s Modulus
Young’s Modulus E (Pa) = Tensile stress/ Tensile strain
Equation for Young’s Modulus
E = Force x length/ Area x change in length
Brittle
Material snaps with no noticeable yield
Breaks soon after reaching its elastic limit
Ductile
Material exhibits plastic behaviour
Breaks long after elastic limit on strain axis
Strong
Little strain for high stress
Steep gradient on stress-strain graph (High YM)
Weak
Large strain for little stress
Shallower gradient on stress-strain graph (Low YM)
Hard
High ultimate tensile stress
Breaks under high stress
Tough
Large amount of energy a material can absorb before it breaks
Large area under the stress-strain graph before material breaks
